Blasting assembly



ug. 7, 1951 T. THoMsoN HAL BLASTING ASSEMBLY Filed July ll. 1947 F/GJ.

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`Patented Aug. 7,1951 'u I l -.f Pf

vrin-esamina assssfmn'r Thomas r`lhomson,

Kenneth Cathro Reid signors to lImperial .C

Kilmarnock, Ayrshire, and

nndee,A Scotland, fasemical Industries Limited, a corporation of Great Britain Application-July 11, 1'94'1', serial No. censos rn creat Britain Julyes'. 194s s crains. (ci. r1oz-an The present invention relatesto Hydron blasting assemblies.

-, `Within recent years the -method of, blasting. with Hydrox has found application 'in the winning of coal from eryand dusty ,mines on account of the exceptional safety characteristics as regards ignition of fire damp and coal dustair mixturesA and the comparatively gentle heave ing action, which favours the 'production of lump coal, thatresult from the method. vIn the. Hy-

drox blasting method there is used as vthe gas.:

producing charge a quantity of Hydro'x powder conne'd in a pressure resisting container having a closure adapted -to yield ata predetermined and considerable pressure sufdcientto for the -decomposition of the accelerated, and the time between the completion ofthe. electric circuit and the occurrence of the blast,.which ismainly the time required 4to complete itself after it has been initiated by the electric powder fuse, is usually only a fractionof aA second; but even by increasing the charge in the electric black powder fuse it has produce a blasting effect -whenthe gaseous and lther -products of reaction emerge into the bore ole.

Hydrox powder'is a mixture in granu lar form consisting essentially of a mixture ofA ammonium-chlorideand sodium nitrite stabilsed by the inclusion of a small percentage of a. faintly alkaline materiah` U. S. Patent No.' 2,038,772 d1scloses a charge of sodium nitrite :andammonium chloride and U. S. Patent 1\To.'2,190,460 d1scloses mixtures of sodium nitrite and ammonium chloride stabilized with magnesium oxide as the "Hydrox powder set forth in this application.

The Hydrox blasting device normally includes a ported discharge head separated from the pressure resisting containerby, means 'of a steel disc adapted to yield a predetermined presrality -of Hydrox blasting assemblies connected together in a single electric circuit.

The object of the present invention is to enable lHyd'rox blasting to be carried out with simultaneousoccurrence of a plurality of shots.- We have now found that the time interval .between the completion of the electric circuit and the Venting of the products of decomposition of the fHydroxpowder can be reduced to a period short enough to enable simultaneous blasting effects to be' obtained from a plurality of Hydrox blasting devices electrically connected together -for simultaneous shot ring when the electricblack powder fuse is provided witlra j sheathing consisting of or comprising a perchlorate, particularly ammonium perchlorate.

sure, so that when the pressure generated in Y this container by the Hydrox powder Abecomes suiciently high the partly gaseous contentsvof -the container rush` into the discharge head, through the ports of which they stream into the bore hole, thus producing the blasting` eect. The Hydrox blasting device normally includes also a nring head through which an electrically v actuated localheating means embedded in the Hydrox powder and adapted toinitiate its decomposition is connected with a source of current external to the device. The possibility of "Hydrox blasting depends -A on the fiact that under atmospheric pressure conditionsthe Hydrox powder is capable of' propagating through Aitself in a self-sustained fashion an exothermic reaction leading to the formation of nitrogen, steam and sodium chicride, when even a small portion' of the mass of the granular mixtureis heated vto a 4suitable temperature. In the Hydroxblastingfassembly the localheating means provided'usually takes the form of an electric black powder fuse', which black powder.

tions encountered in the pressure resisting con? drox powder a charge consisting of or comprisl .ing a perchlorate, particularly ammonium per- 55 may conveniently contain up to. 60 grains of Under the rising :pressure condi- In a. Hydrox blasting device, therefore, ac-

cording to the present invention the electric black powder fuse is provided with a sheathing consisting of., or comprising a perchlorate par#- ticularly ammonium perchlorate.

' It is assumed that in the presence of sufficient perchlorate the black powder fuse burns more i vigorously and thus brings about the quicker4 ignition of the"I -Iydr0x powder. It is also assumed that duringl the burning of said fuse a substantial'amount of hot pechlorate particles isV projected into the surrounding granules oi Hydrox powder.

Tliel invention also comprises a-plurality of like"Hydrox blasting devices electrically 'connected for simultaneous shot firing, said Hy drox` blasting'devices having each in addition. to an electric powder fuse and a chargeof Hyohlorate sheathing said electric powder fuse.4

When the electric powder fuse is actuated; the

hot products of the explosion of the black powder and the combustion of its papercontainer 1 which'include carbonV` monoxide and other oxitainer of the Hydrox blastingdevice, the de'.

composition of the Hydrox powderfis greatly.

disable gases, undergo further oxidation ,with evolution of heatas they come into contact'with the surrounding ammonium perchlorate, `so that' Hydrox powder the aforesaid time intervals t too. great to enable simultav l drox powder what could be obtained by the use of the elecder. VThe items I2 the temperature of the gases is raised. The tem-y perature of the unconsumed ammonium perelectric powder fuse is also raised suillciently to cause it to undergo an exothermic decomposition into. hot gaseous products. Moreover, the actively decomposing particlesof ammonium per-4 of the ammonium perchlorate. The quantity of heat evolved in the form of hot gases is thus cumulatively increased, andthe whole of the ammonium perchlorate is converted into hot 'gaseous products.' Thus apart from the directl heating effects on "Hydrox powder particles struck by the non-gaseous materials, the distributed heating eifects on the particles of Hypermeated by hot gases far exceed tric fuse alone before the cumulative effect of the normal decomposition of the Hydrox powder" becomes effective, and the can thereby be reduced to about or less. A

It is desirable that the electric powder fuse. should contain not less thanaboutthe usual 60 50 milliseconds grains of black powder for a 460 gram 'charge of Hydroxpowder and the amount of 'ammonium perchlorate should be more than the quantity theoretically suillcient to oxidise the gases fronrthe black powder and its paper container to carbon dioxide, water andsulphur dioxide, but not so great scattered in an actively decomposing condition. About 20 grams is a suitable charge'un'der these.A conditions. The Hydrox powder 4is preferably in a granulated` condition. Under these conditions the time interval between completion. oi.' the circuit and the venting of the gases is about- 30 milliseconds..4

The invention is further illustrated in the diagrammatic drawings accompanying the specilication whereof Figure 1 is a longitudinal section of a Hydrox blasting device embodying the invention and matic drawing showing .how a heater unitcomprising an electric powder fusel is ensheathed in a charge of ammonium perchlorate.

In Figure 1, i is the pressure resisting container portion, 2 is the ring head, 3 is the discharge head and 4 is the bursting disc of a Hydroxf blastingv tube. 5 are the insulated leads from the firing head ands seen in greater detain in Figure 2 is the heater unit. .1 is a charge of Hydrox powder N0. 2.

In Figure 2,v 5 are the insulated leads, 6 is a paper tube, 9 is a of a polychloro-naphthalene wax. disc and II is a rate.

Il) is a paper harge oi' ammonium perchloi2 is a paper tube, Il andv il are plugs of polychloro-naphthalene wax, I5. Vis a low tensionelectric fusehead. Isis a charge of black powto I6 constitutes. 60 grain electric powder fuse, and the charge of Aammonium perchlorate H amounts to 20 grams. The

charge 'I of Hydi'ox powder No. 2 in Figure 1 amounts to 460 grams.

We claim:

1. A blasting device ci' the kind comprising a pressure resisting steel contained having a closure adapted to yield at'a predetermined and' delay intervals as to prevent its beingchlorate being scattered by thevexplosion of the a vconsiderable internal gas pressure and con` taining a charge in granular form consisting essentially of a mixture of sodium nitrite and ammonium chloride stabilized by the inclusion of asmall percentage of a faintly alkaline-material and electrically actuated local heating means -wherein the local heating means comprises an l electric black powder 2. A blasting device asset'forth in claim 1 .having a weight of ammonium perchlorate sheathing in excess to that quantity theoretically products resulting from the ignition of the black powder and yet a quantity not so great as to prevent it being scattered in an actively decomposing condition. 1

3. A blasting device as set forth in' claim 1 wherein approximately 60 grains of blackpowder and approximately 20 grams of ammonium perchlorate are present for each 460 of the blasting powder employed.

.-4. A plurality o'f blasting devices as set forth .in claim 1 electrically connected for simultaneous ring.

5. An electric black powder fuse having a sheathing consisting substantially of ammonium in ablasting device of the kind comprising a pressure resisting s teel container having-.a closure adapted to yield at a predetermined and a. considerable internal gas pressure .andcontaining a 'charge in granular consisting. essentially of .a mixture of sodium nitrite. andammonium chloride stabilized bythe inclusion of a small percentage of' faintly Figure 2 is a detailed diagramcork plug and 8 and i1 plugs black .powder surrounded by .alkaline material and an electrically actuated heating means.

6. An electric fuse for use in a blasting device.

of the kind comprising a pressure resisting steel container having a closure adapted to yield at a predetermined-and a considerable internal gas pressure and containing a charge in granular form consisting essentially of :a mixture of sodium nitrite and ammonium chloride stabilized by the inclusion of a small percentage of a alkaline material, said fuse comprising a core oi' a tubular casing, an electrical fuse head imbedded in the core, an ammonium perchlorate sheathing about said casing, and a second tubular casing enclosing said sheathing, each end of the .said casings being sealed.

'I'HOMAS THOMSON.

KENNETH CATHRO REID.

REFERENCES CITED The following references are of'record in the le of this patent:

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